Abstract
In order to improve the signal-to-noise ratio (SNR) of the rough surface crack signal, a magnetic flux leakage (MFL) detection technique based on the magnetic medium lift-off is proposed for the first time. The influence of surface roughness on the crack signal is analyzed based on a simplified model of the workpiece with rough surface. By replacing the air region of the lift-off between the sensor and workpiece with magnetic medium, the leakage magnetic field of the crack and surface roughness are redistributed which results in the change of signals acquired by the sensor. The improvement of the SNR comparing to the widely used air medium lift-off is demonstrated and confirmed through simulation approaches. In addition, the different thickness and relative permeability of the magnetic medium lift-off are analyzed to optimize the improvement method in this paper.
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